Electronic graticule for cathode ray tubes



March 10, 1970 M. E. AUGER. JR 3,

ELECTRONIC GRATICULE FOR CATHODE RAY TUBES Filed June 10, 1968 6Sheets-Sheet 1 I00 IIO I20 T0 VERTICAL MIXER 24 T0 HORIZONLAL MIXER 22MIXER I RING RING COUNTER COUNTER I a2 as HQ 4 MONOSTABLE RAMPMULTIVIBRIIIOP GENERATOR RATE ADJUST 30 v" INVENTOR MEDERIC E. AUGER,JR.

BY @02 @vda FROM SWITCH I6 ATTORNEY March 10, 1970 M. E. AueER, JR

ELECTRONIC GRATICULE FOR cmnom: RAY TUBES 6 Sheets-Sheet 2 Filed June10, 1968 INVENTOR BY MEDERIC E.AUGER,JR. wad,

ATTORNEY @359 ZOEHEQ 2535:

March 10, 1970 M. E. AUGER, JR

ELECTRONIC GRATICULE FOR CATHODE RAY TUBES 6 Sheets-Sheet 5 Filed June10. 1968 VERTICAL AMPLIFIER MIXER WAVEFORM 8 VERTICAL LINE TRACINGCIRCUIT I HORIZONTAL AMPLIFIER HORIZONTAL LINE TRACING CIRCUIT SOURCEATTORNEY 1, 1970 M. E. AUGER. JR

ELECTRONIC GRATICULE FOR CATHODE RAY TUBES 6 Sheets-Sheet 4 Filed June10, 1968 TIME TIME

N 0 N P hnyai o ATTORNEY -FROM MULTIVIBRATOR 32 .QRRING COUNTER 34 y 3%M. E. Auem, JR 3,@,E i

ELECTRONIC GRATICULE FOR CATHODE RAY TUBES Filed June 10, 1968 6Sheets-Sheet 5 To VERTICAL MIXER 24 TO HORIZONTAL MIXER 22 MIXER 76MIXER I I l 4 DISCHARGE PEAK E DETECTOR SW'TCH AND DRIVER w j GATE RAMP/@L+' I I 82 RATE I GEN I PULSE M ADJUST I I SHAPER MONO A I MV. L 72 66sNITcII I4 0 '9' MAIN SYNC.

RESET GATE MAIN SYNC. WAIIEEORM RESET K I x ID. BISTABLE MV. N 56 5 MAINSYNC. l4 SY c RESET sIIIITcH INvEIITOR MEDERIC E. AU6ER,JR.

FROM swITcII I6 BY 4 @WJMH ATTORNEY.

Pig-Mk2}! y 19% M. E. AUGER, JR 35am ELECTRONIC GRATICULE FOR CATHODERAY TUBES Filed June 10, 1968 6 Sheets-Sheet 6 khHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH LQ/l/l/l/l/l/M/l/I/l/l/l/l/I/l/l/l/l/I/I/l/l/l/l/l/1/l/l/l/l/l/\/l/l/lHIIHIIIIHHHI Will 111i TIME INVENTOR MEDERIC E. AUGER,JR.

BY F M ATTORNEY 3,500,115 ELECTRONIC GRATHCULESFOR CATHODE RAY TUBEMederic E. Auger, .lr., Schenectady, N.Y., assignor to General ElectricCompany, a corporation of New York Filed June 10, 1968, Ser. No. 735,648Int. Cl. Htllj 29/70 U.S. Cl. 315-18 4 Claims ABSTRACT OF THE DISCLOSUREA technique and circuitry for the generation of an electronic graticuleand display of such on the screen of a cathode ray tube oscilloscopewith a waveform to be measured thereagainst is based on time-sharingestablished by the production of a cyclical time interval and a numberof smaller time intervals within for the display of vertical lines,horizontal lines and the waveform or waveforms in any permutation. Inone embodiment, the cyclical time interval is established by countingfrom a 60 Hz. signal and the smaller time intervals by energization of aswitch by a signal having the cyclical time interval. The horizontallines may be generated by sweeping the outputs of modified ring countersstepped by an oscillator, the spacing between the lines being determinedby the step amplitude differences in the ring counter outputs. In theremainder of the cyclical time interval, a waveform and the verticallines may be displayed by suitable gating means driven by a time basecircuit. The vertical lines may be repetitively generated by sweepingthe output of a peak detector which converts a series of spikesmodulated by a sweep voltage into a series of step voltages.

BACKGROUND OF THE INVENTION This invention relates generally tograticules or scales for cathode ray tubes and more particularly, to amethod and means for electronically producing such a graticule.

From the days of introduction of Oscilloscopes employing cathode raytubes for signal display and measurement, the accurate and precisemeasurement of waveform levels from visual inspection of the signaltrace has been a roblem. The earliest Oscilloscopes employed anauxiliary transparent plastic window which was placed in front of thecathode ray tube screen. The plastic window had a graticule inscribed onits rear surface and made visible by means of edge illumination. Aserious drawback, however, was that a large parallax error was possiblein visual measurement, due to the thickness of the cathode ray tubeenvelope interposed between the cathode ray tube screen and thetransparent plastic window. In order to make an accurate measurement,the observer had to remain stationary when calibrating the instrumentand measuring the waveform.

More recently, oscilloscope and instrument manufacturers have turned tocathode ray tubes having graticules which are internally scribed in thecathode ray tube screen. As the observer can therefore move freely whilemaking measurements, due to the absence of parallax error, theseinstruments are vastly more convenient to use than those utilizingtransparent plastic windows.

Nevertheless, this advance has brought the problem of inflexibility ofmeasurement. That is, the waveforms traced by the electron beam can bemeasured only against the internally scribed graticule. Where theinternally scribed graticle is linear and the waveform desired to bedisplayed has a logarithmic characteristic, such as would be obtainedfrom a logarithmic amplifier, calibration and measurement of thewaveform cannot be made. Certainly, logarithmic scale could beinternally scribed, but the number of 3,50%,115 Patented Mar. 10, 1970decades thereof would be fixed and the graticule would then be uselessfor linear measurements.

A recent attempt to solve this problem resulted in a device which isexternally attached to the oscilloscope and which projects a graticuleon the face of the cathode ray tube. The graticules may be varied byinserting different transparent slides in the device. However, as withthe earliest Oscilloscopes, this device again may produce a largeparallax error. Further, the device is cumbersome and the resultantgraticule is barely visible, due to poor reflection from the cathode raytube face.

In other art, it has been proposed to generate a series of lines forsimulating in a CRT display an approaching runway. While the techniquesfor producing such lines may be applicable to graticule displays, theydo not allow for the display of both a graticule and a waveform to bemeasured thereagainst.

SUMMARY OF THE INVENTION Therefore, it is an object of this invention toprovide a graticule for use in cathode ray tube measurements whichproduces no parallax error and which may be varied for differentmeasurements.

It is a further object of this invention to provide such a graticulewhich may include logarithmic, linear or other types of scales, eithersingly or in combination.

Briefly, these objects are achieved, according to one embodiment of theinvention, by electronically producing signals by time-sharingtechniques which include components representative of the wave-form tobe displayed and of the horizontal and vertical lines of the graticule,then applying the signals sequentially to the deflection means of thecathode ray tube so that both the waveform and the graticule appear tothe eye to be superimposed on the cathode ray tube screen.

BRIEF DESCRIPTION OF THE DRAWINGS The subject matter of the invention isparticularly pointed out and distinctly claimed in the concludingportion of the specification. For a complete understanding of anemboditment of the invention together with further objects andadvantages thereof, reference should be made to the followingdescription taken in conjunction with the accompanying drawings inwhich:

FIGURE 1 is a front view of a cathode ray tube screen showing thereonthe electronic graticule of this invention and a superimposed waveform;

FIGURE 2 is a diagram showing the waveforms of the signals applied tothe deflection means of a cathode ray tube for one embodiment ofgraticule and waveform dis- P y;

FIGURE 3 illustrates a block diagram of a means for producing thesesignals;

FIGURE 4 is a block diagram of a means for producing the horizontallines of the graticule;

FIGURE 5 is a timing diagram to be used with FIG- URE 4;

FIGURE 6 is a schematic diagram of an element of the means in FIGURE 4;

FIGURE 7 shows a block diagram of a means for displaying the waveformand the vertical lines of the graticule:

FIGURE 8 is a timing diagram to be used with FIG- URE 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGURE 1, a sample electronicgraticule produced according to the teachings of this invention isillustrated. The graticule comprises a plurality of spaced, verticallines which are intersected by a plurality of spaced, horizontal lines.Each line is traced n the phosphor screen of the cathode ray tube,hereinafter CRT, by means of signals applied to the deflection meansthereof. The particular graticule illustrated in FIGURE 1 includeslinear spacing of the vertical lines and a repetitive logarithmicspacing of the horizontal lines at 1, 2, 3, 4, 6 and 8 divisions. But,this invention is in no way limited to such a graticule; for instance,the graticule may comprise logarithmic spacing of the vertical lines andlinear spacing of the horizontal lines. Furthermore, this invention hassuch flexibility that practically any spacing between the lines can beaccomplished.

The waveform to be displayed is normally traced so as to appearsuperimposed on the graticule by a time-sharing technique. The signalsnecessary to accomplish both waveform and graticule tracing areillustrated in FIGURE 2.

FIGURE 2a depicts waveforms of the signals applied to the horizontaldeflection means of the CRT and FIG- URE 2b shows the signals applied tothe vertical deflection means. The display of both the graticule and thewaveform is cyclical, repeating every T seconds. The interval T may bedivided into three smaller intervals:

( 1) An interval 1,; (2) An interval 1 (3) An interval t In FIGURE 2,the horizontal lines of the graticule are displayed during the firsttime interval, the waveform or information signal is displayed duringthe second and the vertical lines during the third. As will be moreclearly seen when the formation of the signals to produce such a displayis explained, the invention is not limited to such a time sequence, butindeed contemplates any permutation thereof.

Again referring to the graph of FIGURE 2, the horizontal lines areformed during the interval 21., by applying to the vertical deflectionmeans a series of step voltages, progression through the series beingmade with respect to time. Simultaneously, the electron beam is swepthorizontally for each step voltage by a varying sweep voltage applied tothe horizontal deflection means.

More particularly, the logarithmic scale of FIGURE 1 may be generated byapplying a voltage having a level 1 to the vertical deflection means andsweeping the beam by means of a simultaneous sw ep voltage applied tothe horizontal deflection means. The lines 2, 3, 4, 6 and 8 are formedin a similar manner, the spacing between the voltages applied to thevertical deflection means determining the vertical scale divisions ofthe horizontal lines. The logarithmic characteristic may be reiteratedat 10, 100, 1000, and so forth, by applying a fixed voltagerepresentative of the decade and repeating the step voltage variation asdepicted in FIGURE 2.

At the end of the first time interval the display of the horizontallines is terminated. Thereafter, during the sec- 0nd time interval 1 thewaveform or information signal is displayed by applying this waveform tothe vertical deflection means and sweeping the beam conventionally by asingle sweep voltage applied to the horizontal deflection means. At theend of the second time interval, the waveform display is ended and thethird time interval is initiated wherein the vertical lines may bedisplayed in the same manner as were the horizontal lines, with the stepvoltages now being applied to the horizontal deflection means and thesweep voltages to the vertical deflection means. In FIGURE 2, the stepsare equidistantly spaced to display linear scale divisions of thevertical lines. Moreover, the vertical lines have been retraced a numberof times, the purpose of which will be fully explained hereinafter. Atthe completion of the third time interval, the cycle T of graticule andwaveform display repeats.

It should be noted that display of each portion of the graticule anddisplay of the waveform is accomplished only for a time interval t,smallpr than the total cyclical i te val I- One sen en ent alue f he tme i e v I 4 may be that obtained from a 60-cycle sine wave, orapproximately thirty-five milliseconds. For convenience, the first timeinterval may equal one-half of the total interval T. In order to avoid aflickering display at this low duty cycle, a CRT may be used whosephosphors have a high persistence for a given amount of voltageexcitation.

Necessarily, such a long interval T places limitations upon thetransient waveform displaying ability of the oscilloscope, for the timeinterval t is but a small portion of the total time interval T. Thus, along time exists in which no signal can be displayed. It is toward thisresult that other embodiments of the invention may be drawn which willbe described hereinafter, For purposes of illustration, the teachings ofthis invention will be further described in terms of the embodimentillustrated in FIG- URE 2. Such a method of display is most useful whenthe waveform to be displayed is that obtained from a pulsegeneratingcircuit for applications such as shock-excited, ultrasonic transducersor modulators in which the pulse originates at the initiation of timeinterval 1 In addition, the embodiment of FIGURE 2 is eminently suitablefor display of steady state signals or those whose transient times aresignificantly longer than that of the time interval T, which may bemilliseconds.

One may now see the reason for repetitive display of the vertical linesin the time interval t Although the eye acts as an effective integratorof the varying graticule and waveform displays, it has been found thatpersistence problems may be encountered with conventional cathode raytubes. Particularly is this so when the electron beam is swept acrossthe phosphor screen at a high rate. It can be said that in FIGURE 2,wherein the first time interval t =T/2 and the sum of the second andthird time intervals also equals T/2, time sharing between the waveformdisplay and vertical line display results in a decreased time of sweepof any one particular line as contrasted with the sweep time of ahorizontal line during the first time interval. Therefore, the phosphorsin each line may not be excited to a degree suflicient to effectpersistence for the rest of the third time interval. To obviate thisproblem, each particular line may be swept a number of times.

In the general case, the number of lines displayed in both the verticaland horizontal scales may be varied by changing either the frequency ofline display within each individual time interval or the magnitude ofeach step voltage applied to the deflection means. In a practical case,the frequency of line display is fixed and the number of lines arevaried by adjusting the final amplification of the step voltages beforeapplication to the deflection means.

Turning now to FIGURE 3, a means for implementation of the methodillustrated by the graph of FIGURE 2 is shown. A cathode ray tube 1includes a phosphor screen 2 on an inner surface of the glass envelopethereof, a vertical deflection means comprising a pair of deflectionplates having terminals 3 and a horizontal deflection means comprising apair of plates having terminals 4. Connected to the terminals 3 arepushpull outputs from a vertical amplifier 5; connected to the terminals4 are push-pull outputs from a horizontal amplifier 6. The elements 1through 6 may comprise elements of any currently marketed, standardoscilloscope or they may be integrated with a fraticule generation means10 which has power and signal input from an alternating current source12. The frequency of source 12 may comprise Hz or power line frequency.The signal from source 12 is fed to a main sync circuit 14 which mayeither count up or count down from the frequency of the source 12 toprovide an output signal which has a time interval T. As previouslymentioned, T serves as the main time basis for establishing time sharingof the graticule and waveform display. In a pre-. ferred embodiment,main sync 14 provides a 30 Hz. square a e at its outp t t r inal hi ison ect d in turn to a switch circuit 16. An electronic switch, such as aflip-flop or bistable multivibrator, may comprise switch 16 but anyother means for producing two separate output signals at the initiationof each half-cycle of the square wave from main sync 14 could be used.In FIGURE 2, one switch output is provided during the first timeinterval t the other switch output is provided during the second andthird time intervals t and r Alternately, main sync 14, together withswitch 16, may divide the signal from source 12 into a plurality ofportions so that flexibility in the display may be accomplished.

One output from switch 16 is fed to a horizontal line tracing circuit 13and the other output from switch 16 is fed to a waveform or informationsignal and vertical line tracing circuit 20. Horizontal line tracingcircuit 18 produces both horizontal and vertical output voltages whichare fed, respectively, to a horizontal mixer 22 and a vertical mixer 24.Horizontal mixer 22 is connected to the input of horizontal amplifier 6and vertical mixer 24 is connected to the input of vertical amplifier 5.In like vein, the waveform and vertical line tracing circuit has bothhorizontal and vertical output voltages which are connected in turn tohorizontal mixer 22 and vertical mixer 24 and thence to horizontalamplifier 6 and vertical amplifier 5. Finally, circuit 20* has thewaveform to be displayed as an input thereof.

In operation, switch 16 provides, at the beginning of the output signalfrom main sync 14, or the beginning of t an output signal to horizontalline tracing circuit 18. Thereafter, the horizontal circuit 18 producesthe horizontal lines of FIGURE 2. At the end of t and the beginning of tthe output signal is removed from horizontal circuit 18 and applied towaveform and vertical line tracing circuit 20 which thereafter displaysthe waveform and vertical lines until the end of r at which time switch16 removes the output signal from circuit 20 and reapplies it to circuit18 to repeat the display. Mixers 22 and 24 perform a simple function ofcoupling the voltages from circuits 1 S and 29 to the appropriate inputsof the oscilloscope amplifiers 5 and 6.

Variations on the circuitry of FIGURE 3 can easily be visualized; forinstance, the waveform could be displayed during the first time intervalt by coupling it to amplifiers 5 and 6 through the horizontal linetracing circuit 18 instead of circuit 20. Or, main sync 14 and switch 16could provide four distinct signals in each time interval T. In responseto the first signal, the horizontal line tracing circuit 18 could beenergized. In response to the second and third signals, the waveformcould be applied to the amplifiers 5, 6 through a separate gatingcircuit energized by switch 16. Finally, during the time interval of thefourth signal, the vertical line tracing circuit 20 could be energized.

Appreciation of this invention then reveals no restriction on the broadaspect of graticule and waveform display utilizing time sharingtechniques. The particular method and means used will depend on thenature of the waveform; where the main sync 14 and switch 16 providedfour signals per time interval T, display of transient waveforms wouldbe facilitated. On the other hand, the method in FIGURE 2 and thecircuitry of FIGURE 3 provide a more flexible display of the graticule.

Returning now to FIGURE 3, the voltages present at the outputs of mixers22 and 24 are those represented by the waveshapes of FIGURE 2. Thenumber and relative magnitude of the graticule lines and of thewaveforms actually displayed depend on the gain of amplifiers 5 an 6. Byknowing the magnitude of the output voltages from mixers 22 and 24 andthe gain of the amplifiers 5 and 6, the graticule can be calibrated.Thereafter, the waveform may be measured thereagainst by visualinspection.

Means are pictured in FIGURE 4 for implementing the horizontal linetracing circuit 18, although these means could equally be applicable todisplay of vertical lines in embodiments other than those illustrated inFIGURE 3. The output signal from switch 16 is applied to a sync switch30 which in turn connects a positive voltage supply V+ to a monostablemultivibrator or oscillator 32. Oscillator 32 then produces a pluralityof pulses at a predetermined repetition rate which are coupled both to aring counter 34 and to a ramp generator 36 which has one output coupledback to oscillator 32. The frequency at which changes in the voltagesteps applied to the vertical deflection means of the CRT, asillustrated in FIGURE 2, is governed by the repetition rate of thepulses from oscillator 32. Ramp generator 36 converts these pulses intosweep voltages and may be adjusted by means of a rate adjust control sothat one complete sweep is made for every step. The sweep voltages arecoupled through horizontal mixer 22 to horizontal amplifier 6 and theirwaveforms appear as seen in FIGURE 2a during the first time interval tWhen the pulses from oscillator 32 are applied thereto, ring counter 34produces the step voltages illustrated in FIGURE 2b in the first timeinterval t Simply, ring counter 34 produces a slightly higher voltage atits output terminal for each pulse; the number of step increases beforeresetting is determined by the number of stages in the ring counter. Byvarying the step voltage produced by each stage as hereinafter related,the number of lines to be displayed can be changed. Spacing between stepvoltages is accomplished by means internal to the ring counter, alsodescribed hereinafter.

The output from ring counter 34 is fed to a mixer 38 and to a secondring counter 40 which has as a resetting input a second output from syncswitch 30. Ring counter 40 in turn has its output coupled to mixer 38Whose output is connected through vertical mixer 24 to verticalamplifier 5. By means of this circuitry, logarithmic or other scales canbe easily displayed. For instance, the spacing and number of lineswithin a single decade of a log scale can be varied by adjustment ofring counter 34. When ring counter 34 resets from its highest value ofvoltage, ring counter 40 is shifted thereby to its next highest voltageoutput. Thereafter, ring counter 34 reiterates its voltage steps. Bycombining these voltage in mixer 33, an ascending staircase waveform canbe produced.

Reference should be made to FIGURE 5 for depiction of outputs from ringcounters 34 and 40. FIGURE 5a shows the output voltage from ring counter34 when that counter has been adjusted to provied a logarithmic decadewith steps at l, 2, 3, 4, 6 and 8. FIGURE 5b shows the output voltagefrom ring counter 40 when that counter has been adjusted to provideuniform decade steps at 1, 10, 100, 1000, etc. The 1 step of counter 34can be chosen at a convenient reference level; thereafter, when theoutput from ring counter 34 shifts to the 1 step, ring counter 40advances to the next decade. By summation of these voltages in mixer38-, the waveform of FIGURE 2b can be produced.

Ring counters 34 and 41) may comprise any of those well-known to theart, with slight modification. Such a modified counter is illustrated inFIGURE 6 and comprises a plurality of transistors Q Q Q The number ofsuch transistors depends on the number of ring counter stages and thusupon the maximum number of steps to be produced thereby. Each of thetransistors Q through Q has its emitter connected to a reference bus -41which is in turn connected to a conducting electrode of a switch, suchas transistor 42. The other conducting terminal of transistor 42 iscoupled to a source of reference potential, such as ground. The baseelectrodes of transistors Q through Q are connected to a first biasingvoltage supply V by appropriate biasing resistors R through R Inaddition, the collector of each transistor Q through Q is coupled to thebase of an immediately succeeding transistor in the ring by a capacitorC through C Disposed between a second biasing voltage supply V and thecollectors of transistors Q through Q are potentiometers P through Pwhose taps are connected to a common output point 43 through diodes Dthrough D Finally, an input to the ring counter is coupled to theelectrode of transistor 42 through a resistor 44.

In operation, the reception of a pulse at the input, as from eithermultivibrator 32 or ring counter 34, places transistor 42 in anon-conducting state as long as the input pulse is present. Each pulsethus steps the ring counter from one count state to another. Assumingthat all transistors Q through Q have been set in a nonconductingcondition, and that transistor Q is conducting, non-conduction oftransistor 42 turns off transistor Q The anode voltage of Q rises to thevalue of supply V The positive transient produced thereby is coupled toQ by means of capacitor C Meanwhile, the input pulse is removed andtransistor 42 is placed in a conducting state. If transistor 42 conductsbefore the transient voltage coupled to Q has decayed below the turn-onvoltage of Q Q is placed in a conducting condition. In thi manner,transistor 42 steps conducting states around the ring counter at a ratedetermined by multivibrator 32 or ring counter 34.

The different step voltages of the ring counter output may be obtainedby adjusting the setting of potentiometers P through P thereby varyingthe voltage dropped thereacross and supplied to common point 43 uponconduction of the associated transistors Q through Q The maxi mum numberof lines displayed is dependent on the number of stages in each ringcounter. If a lesser number is desired to be displayed, as within alogarithmic decade, the potentiometers of the two or more adjacentstages may be adjusted to provide the same step voltage so that one lineis thereby retraced.

Referring again to FIG. 4, switch 16 removes its output signal from syncswitch at the end of interval I sync switch 30 in turn removes thevoltage V+ from oscillator 32 and provides a reset signal to ringcounter 40.

In FIG. 7, a means for the implementation of the graph of FIG. 2 duringintervals t and r is illustrated. This means may comprise block 20 ofFIG. 3.

At the end of first time interval t as previously described, switch 16provides an output signal to circuit 20. In FIG. 7, this output signalis applied directly to a sync switch which then connects the positivevoltage supply V+ to a time base circuit 51 for providing a time basethroughout the second and third time intervals via a time delay 56, abistable multivibrator 54 and a switch 55. Time base circuit 51comprises a monostable multivibrator 52 and a ramp generator 53 whichare interconnected in the same manner as are monostable multivibrator 32and ramp generator 36 of FIG. 4. Monostable multivibrator 52 in turn hasits output connected to an input of a bistable multivibrator 57, a timedelay 59, and a pulse shaper 9% In this embodiment, the second and thirdtime intervals are derived from the output of time base circuit 51. Tothis end, switch 55 provides V+ to energize the monostable multivibrator52. Monostable multivibrator 52 controls ramp generator 53 whose outputis fed to gates 64 and 62. Bistable multivibrator 57 is turned on at theend of period 2, by the Main Sync Reset 14 and i turned off at the endof period t by the monostable multivibrator 52. The output of bistablemultivibrator 57 feeds gates 60 and 64 to allow their respective signalsto pass only during the second time period t Gate 60 thus passes thewave form 63 to mixer 76 and gate 64 thus passes only the 1st rampgenerated by ramp generator 53 to mixer 78. In like manner monostablemultivibrator 52 turns on switch 66 via time delay 59 and bistablemultivibrator 61 which applies V+ to energize monostable multivibrator72 which is coupled to ramp generator 74. The time base 68 isindependent of time base 51 except for synchronization. The inputs togate 62 are the square wave from bistable multivibrator 57 and the rampproduced at the output of ramp generator 53. The output of gate 62 istherefore all the ramps from ramp generator 53 with the exception of thefirst one. This is now period r The output of gate 62 is coupled to gateThe output of ramp generator 74 is connected to mixer 76. The output ofmonostable multivibrator 72 is connected to a pulse shaper 82 whoseoutput controls the gate 89. In turn, the output of gate 80 is connectedto a peak detector and driver 84 whose output is connected to mixer 76.Driver 84 is controlled by a discharge switch 86 which has as an inputthereto the output of a pulse shaper 99 controlled by monostablemultivibrator 52. Finally the output of mixer 76 is coupled tohorizontal mixer 22 and the output of mixer 73 is coupled to verticalmixer 24.

To understand how the circuit of FIG. 7 functions to produce thevoltages of FIG. 2, reference should be made to the timing chart of FIG.8 in which relative magnitudes of the signals illustrated have beenignored. The plot of FIG. 8 begins at some arbitrary time within thefirst time interval t and ends at an arbitrary time within the thirdtime interval t FIG. 8a shows the output signal applied to the input ofsync switch 50 from switch circuit 16. FIG. 8b shows the voltage V4-which energizes monostable multivibrator 52 at the beginning of thesecond time interval t FIG, 8c shows the voltage V+ which energizes gate62 at a time within the second time interval as determined by bistablemultivibrator 57. FIG. 8d illustrates the output of multivibrator 52which comprises a plurality of recurrent, positive pulses having arepetition rate which is greater than that of the pulse output fromswitch circuit 16. The duration of the first recurrent pulse equals thatof t and the pulses continue throughout the third interval t FIG. 8aillustrates the ramp output voltages obtained from ramp generator 53 andcoupled to the inputs of gates 62 and 64. The rate adjust control oframp generator 53 is varied to suit the time display, l to observe thewaveform (in much the same manner as ramp generator 36 is adjusted withrespect to the pulses from oscillator or multivibrator 32).

In FIG. 8], the output of bistable multivibrator 57 comprises only thefirst pulse from monostable multivibrator 52, or that marking the secondinterval t The second and all succeeding pulses are blocked by gate 64which is controlled by 57. To accomplish this result, gate 64 maycomprise any circuitry which, upon absence of a voltage such as V+,allows a pulse to be coupled from its input to its output and which,upon cessation of that pulse and a prior application of the voltage V+blocks all succeeding pulses from its output.

This pulse from bistable multivibrator 57 controls gates 60, 62 and 64.

FIG. 8g shows the output of gate 60 for a typical waveform applied tothe input thereof. It should be noted that the input waveform is coupledto the output thereof only during the second time interval 11,, or, theduration of the pulse from bistable multivibrator 57. Similarly, FIG. 8hillustrates the output from gate 64 which comprises one sweep of theramp voltage from ramp generator 53 during the second time interval t Bymeans of mixers 76 annd 24, the waveform at the output of gate 60 iscoupled to the vertical amplifier 5 and thus to the vertical deflectionmeans terminals 3 of the CRT 1. The sweep voltage appearing at theoutput of gate 64 is likewise coupled through mixers 78 and 22 tohorizontal amplifier 6 and thus to the horizontal deflection meansterminals 4 of CRT 1. In this manner, the waveform is displayed duringthe second time interval t and the waveforms in FIGS. 8g and 8hcorrespond exactly to the waveforms of FIGS. 2b and 2a during the secondtime interval.

FIG. 81 shows the output pulses from multivibrator 52, beginning at theinitiation of time interval t and recurring thereafter throughout theinterval, terminating at end of t FIG. 8i shows the output of gate 62which comprises the recurring sweep voltage from ramp generator 53,beginning at the initiation of time interval z, and recurring thereafterthroughout the interval. FIGS. 8g and 811 show that during the thirdtime interval, no signal is present at the outputs of gates 60 and 64.Therefore, by means of bistable multivibrator 57, gates 60 and 64 assurethat the waveform only is displayed during the second time interval andthat thereafter during the third time interval the waveform and a sweepsignal or another waveform are blocked from the deflection terminals 3,4 of the CRT 1 and that voltages representing the vertical lines may beproduced.

Pulses from monostable multivibrator 52 energize sync switch 66 via thevariable time delay 59 and bistable multivibrator 61 to apply thevoltage V+ to time base circuit 68. During this pulse and duringsucceeding pulses, monostable rnultivibrator 72 and ramp generator '74of time base circuit 68 oscillate at a frequency higher than that oftime base circuit 51. The number of pulses produced by multivibrator 72during one pulse from multivibrator 52 determines the maximum number ofvertical lines which can be displayed. The pulses from multivibrator 72are illustrated in FIGURE 8k, and by comparison with FIGURE 8i, ten suchpulses are produced for one pulse from multivibrator 52. Therefore, themaximum number of lines displayed in this embodiment would be ten, as isthe case with the voltages of FIGURE 2.

Ramp generator 74 is adjusted by means of its rate adjust control toprovide one sweep voltage for every pulse from multivibrator 72. Thesesweep voltages are illustrated in FIGURE 81 and are coupled to thevertical deflection means terminals 3 through mixers 76 and 24 andvertical amplifier 6. The pulses from monostable multivibrator 72 areconnected to pulse shaper 82 whose output is illustrated in FIGURE 8m.Pulses shaper 82 may comprise any circuitry for converting each of thepulses from multivibrator 72 into a sharp, relatively large amplitudespike. For instance, pulse shaper 32 could include any knowndifferentiating circuiting. The plurality of spikes in FIGURE 8m areapplied to the gate terminal of permissive gate 80. As the sweepvoltages illustrated in FIGURE 81' are applied to the input of gate 80during the third time interval, the output from gate 80 comprises aseries of spikes occurring at a rate equal to that present at the gateterminal thereof and varying in amplitude proportionally to theinstantaneous value of each sweep voltage. FIGURE 8n depicts the output.These spikes present at the output of gate 80 are in turn fed to thepeak detector and driver 84 which converts each spike into a stepvoltage proportional to the maximum amplitude thereof, as illustrated inFIGURE 80. This output is fed to the horizontal deflection meansterminals 4 through mixers 78 and 22 and horizontal amplifier 6.Therefore, the waveform appearing at FIG- URE 80 is identical with thatappearing in FIGURE 2a during the third time interval t At the beginningof time interval t the pulses from monostable multivibrator 52 are alsocoupled to pulse shaper 98 which differentiates these pulses into aseries of spikes in the same manner as does pulse shaper 82 with respectto the output of multivibrator 72. The output of pulse shaper 90 is seenin FIGURE 8p and comprises a sharp spike occurring at a rate equal tothat of mlutivibrator 52. These spikes in turn energize discharge switch85 to provide a discharge path for the voltage accumulated in peakdetector and driver 84 at those times so that the step voltageprogression may be reiterated in order to retrace each of the verticallines in the display.

Therefore, the circuitry illustrated in FIGURE 7 provides a means forimplementation of a technique using time sharing between the waveformand line displays. In addition to the fact that recurrent traces aremade 10 of the vertical lines to insure persistence thereof, thecircuitry of FIGURE 7 also provides that the vertical lines accuratelydepict time markers without distortion thereof. For instance, if thesimple step voltage display used for the horizontal lines in theembodiment of FIG- URES 4, 5 and 6 were used for display of timemarkers, any departure from a linear progression thereof would producecorresponding errors in spacing of the time markers. When the markersare displayed with respect to a timebase, such as circuit 68 of FIGURE7, this problem is eliminated. Of course, if time accuracy were desiredin the display of horizontal lines, the circuitry of FIG- URE 4 could bereplaced by the circuitry of FIGURE 7. If time accuracy were required inthe display of the entire graticule, the circuitry of FIGURE 7 alonecould be used, the output voltages thereof being coupled to thedeflection means of the CRT 1 through a switch which would be energizedby switch circuit 16.

The embodiment of FIGURE 7 uses a fixed unit of time which isestablished by time base circuit 51 for determining time sharing betweenthe display of the waveform and of the vertical lines. However, thistime sharing could be established by obtaining a sync signal from thewaveform by trigger means well known to the art, particularly where thewavefrom were a highly transient signal. To implement this technique,the time base circuit 51 could be replaced by the trigger means andgates 60, 62 and and 64 could be designed to alternately display thewaveform and the lines.

On the other hand, if time accuracy were not especially important,triggering could again be obtained from the waveform and applied to astep voltage generator circuit, such as that illustrated in FIGURES 4and 6, for display of the entire graticule. Time sharing could then beaccomplished by a simple gating means coupling the waveform to themixers, amplifiers and deflection means during certain portions of thecycle T.

Finally, it would not be necessary to provide a sweep voltage throughgate 64 to the vertical deflection means if two waveforms were desiredto be displayed simultaneously, such as in Lissajous figures; onewaveform could be applied to gate 60 and the other to gate 64. Ofcourse, such a means of display would be accurate only if both waveformswere nontransient but it can clearly be seen that the variations of theembodiment just mentioned for display of transient signals could beapplied with equal facility to the display of two transient waveforms,the time base for time sharing being established by triggering signalobtained from either or both of the waveforms.

From the foregoing specification, it should be clearly recognized bythose skilled in the art that this invention is not limited to thespecific methods and means illustrated, but is intended to encompass thebroad aspect of utilizing time sharing techniques in the display on acathode ray tube screen of a waveform or waveforms and of a graticule onwhich measurement of the waveforms is to be made. The circuitryillustrated in the foregoing specification illustrates merely apreferable embodiment from the standpoint of steady state waveforms orthose having a low repetition rate, as well as possessing otheradditional advantages such as accurate establishment of time markers andpersistence of vertical lines displayed. However, it is to be understoodby those skilled in the art that the invention is not limited theretoand is intended to be bounded only by the limits of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A graticule and waveform display means for use with a cathode rayoscilloscope including a cathode ray tube having horizontal and verticaldeflection means, a horizontal input coupled to the horizontaldeflection means through a horizontal amplifier, and a vertical input Llli coupled to the vertical deflection means through a verticalamplifier, comprising:

(a) means providing a first signal having a cyclical time interval;

(b) means coupled to said first signal, dividing said ode ray tubeduring a portion of the cyclical time interval and the waveforms may bedisplayed during the remainder of said cyclical time interval.

12 being disposed between the other conducting electrode of one of saidsemiconductor switching devices and the control electrode of animmediately suceeding one of said semiconductor switching devices; (c) abiasing voltage supply;

cyclical time interval into a plurality of shorter time a (d) aplurality of potentiometers, each of said potcn intervals and producinga separate output pulse for tiometers being connected between the otherconeach of said shorter intervals; ducting electrode of one of saidsemiconductor (c) vertical line tracing means energized by saidoutswitching devices and said biasing voltage supply;

put pulses throughout at least one of said shorter (e) a plurality ofunilateral conducting means conintervals to produce at its horizontaloutput a series nected from the taps of said potentiometers to a offirst step voltages, wherein changes in the step common output point;amplitudes thereof occur with respect to time, the (f) asource ofreference potential; spacing between the step amplitudes being deter-(g) a second semiconductor switching means having mined by thehorizontal scale divisions desired, and 1,3 its conducting electrodesconnected to the reference to produce at its vertical output a firstsweep voltage bus and said source of reference potential and its foreach of said first step voltages; control electrode connected to theinput of said first (d) horizontal line tracing means energized by saidor second ring counters, whereby, either of said first output pulsesthroughout at least another of said or second step voltages are obtainedat the output shorter intervals to produce at its vertical output apoint, the spacing between step voltage amplitudes series of second stepvoltages, wherein changes in the being determined by adjustment of saidpotentiostep amplitudes thereof occur with respect to time, meters. thespacing between the step amplitudes being deter- 3. A graticule andwaveform display means for use mined by the vertical scale divisionsdesired, and to with a cathode ray oscilloscope including a cathode rayproduce at its horizontal output a second sweep tube having horizontaland vertical deflection means, a voltage for each of said second stepvoltages; horizontal input coupled to the horizontal deflection means(e) each of said vertical and horizontal line tracing through ahorizontal amplifier, and a vertical input coumeans comprising pled tothe vertical deflection means through a vertical (i) an oscillatoractuated by one of said output amplifier, comprising:

pulses to thereby produce a plurality of first (a) means providing afirst signal having cyclical time pulses at a predetermined rate,interval;

(ii) a ramp generator coupled to said oscillator (b) means coupled tosaid first signal, dividing said to produce one of said first or secondsweep cyclical time interval into a plurality of shorter time voltagesfor each of said first pulses, and intervals and producing a separateoutput pulse for (iii) means including a first ring counter having eachof said shorter intervals;

its input coupled to said oscillator and produc- (c) vertical linetracing means energized by said outing at its output a series of thirdstep voltages put pulses throughout at least one of said shorter whosestep amplitudes reiterate with respect to intervals to produce at itshorizontal output a series time, the spacing between the step amplitudesof first step voltages, wherein changes in the step being determined bythe horizontal or vertical amplitudes thereof occur with respect totime, the scale divisions desired Within the reiteration, a spacingbetween the step amplitudes being detersecond ring counter having itsinput coupled t mined by the horizontal scale divisions desired, and theoutput of said first ring counter and producto produce at its verticaloutput a first sweep voltage ing at its output a series of fourth stepvoltages for each of said first step voltages; whose step amplitudeschange with respect to (d) horizontal line tracing means energized bysaid outeach reiteration of said first ring counter output, put pulsesthroughout at least another of said shorter and a mixer having as inputsthereto the outputs intervals to produce at its vertical output a seriesof of said first and second ring counters and prosecond step voltages,wherein changes in the step ducing at its output either of said first orsecond amplitudes thereof occur with respect to time, the step voltages,spacing between the step amplitudes being deter- (iv) said means beingcoupled to said oscillator mined by the vertical scale divisionsdesired, and to to produce one of said first or second step voltproduceat its horizontal output a second sweep voltages for each of said firstpulses; age for each of said second step voltages;

(f) waveform gating means, energized by the output (e) at least one ofsaid vertical or horizontal line tracpulses during the remainder of saidshorter intervals ing means comprising in said cyclical interval, havingas inputs thereto the (i) a first time base circuit which is energizedby waveforms to be displayed and coupling said waveone of said outputpulses and which produces forms to its horizontal and vertical outputs;and at its outputs a plurality of second pulses and a (g) means couplingthe horizontal and vertical outputs third sweep voltage for each of saidsecond of vertical line tracing means, said horizontal line pulses,tracing means and said waveform gating means to (ii) a second time basecircuit which is energized respective horizontal and vertical inputs ofthe cathby each of said second pulses and which proode ray oscilloscope,whereby vertical and horizonduces at its outputs a plurality of thirdpulses tal lines may be displayed on the screen of the cath- G whichoccur at a rate greater than that of said second pulses and either ofsaid first or said second sweep voltages for each of said third pulses,(iii) a pulse shaper converting said plurality of 2. The graticule andwaveform display means of claim 1 wherein each of said first and secondring counters comprises: 79

(a) a plurality of semiconductor switching devices,

each of said semiconductor switching devices having one of itsconducting electrodes connected to a reference bus;

(b) a plurality of capacitors, each of said capacitors third pulses intoa corresponding plurality of first spikes,

(iv) first gating means having as an input thereto said third sweepvoltages and having as an input to a gating terminal thereof saidplurality of first spikes, whereby said first gating means produces atits output a plurality of second spikes which occur at a rate equal tothat of said first spikes and which occur at a rate equal to that ofsaid first spikes and which vary in amplitude proportionately to theinstantaneous value of each of said third sweep voltages,

(v) peak detector and driver means producing from said second spikeseither of said first or second step voltages, and

(vi) means for discharging said peak detector and driver means uponreception of each of said second pulses;

(f) waveform gating means, energized by the output pulses during theremainder of said shorter intervals in said cyclical interval, having asinputs thereto the waveforms to be displayed and coupling said waveformsto its horizontal and vertical outputs; and

(g) means coupling the horizontal and vertical outputs of said verticalline tracing means, said horizontal line tracing means and said waveformgating means to respective horizontal and vertical inputs of the cathoderay oscilloscope, whereby vertical and horizontal lines may be displayedon the screen of the cathode ray tube during a portion of the cyclicaltime interval and the waveforms may be displayed during the remainder ofsaid cyclical time interval.

4. The graticule and waveform display means of claim 3 wherein saidvertical or horizontal line tracing means and said waveform gating meansare combined, further comprising:

(a) switch means having as an input thereto said plu rality of secondpulses, said switch means being controlled by one of said output pulsesto produce a control signal at its output having a time durationcorresponding to the first of said plurality of second pulses;

(b) second and third gating means having said control signal coupled totheir gating terminals and blocking respectively said second pulses andsaid third sweep voltages from their outputs when said control signal ispresent at their gating terminals;

(c) fourth gating means having said control signal coupled to its gatingterminal and permitting the first of said third sweep voltages to becoupled to its output when said control signal is present at its gatingterminal;

(d) said control signal also being applied to the gating terminal ofsaid waveform gating means to permit the waveform to be coupled to itsoutput only when said control signal is present;

(e) means coupling said third gating means to said second gating means;

(f) means coupling said second gating means to said second time basecircuit;

(g) means coupling said fourth gating means to the horizontal output ofsaid waveform gating means;

(h) whereby, the waveform is displayed throughout the first of saidsecond pulses and the lines are displayed during the remainder of saidshorter time interval.

References Cited UNITED STATES PATENTS 2,504,852 4/1950 Lewis 315-242,666,868 1/1954 McMillan 315-22 2,741,722 4/1956 Shields 315-222,967,263 1/ 1961 Steinhauser 315-26 3,404,309 10/1968 Massel et a1.315-18 RODNEY D. BENNETT, 111., Primary Examiner I. G. BAXTER, AssistantExaminer US. Cl. X.R. 315-24

